Process for the oxidation of unsaturated hydrocarbons

ABSTRACT

The invention relates to a process for the oxidation of unsaturated hydrocarbons, wherein an unsaturated hydrocarbon, an oxygen-containing oxidizing agent, a palladium complex as the catalyst containing a ligand of the formula (I)  
                 
wherein R is a saturated, halogenated alkyl radical having from about 1 to about 20 carbon atoms, and optionally auxiliary substances in a liquid phase based on (α1) from about 10 to about 100 wt. % of a protic polar solvent and (α2) from 0 to about 90 wt. % of an aprotic polar solvent, the sum of components (α1) and (α2) being about 100 wt. %, at a temperature in a range from about 30 to about 300° C. under a pressure in a range from about 1 to about 200 bar, such that a liquid phase containing oxygen-containing hydrocarbons is obtained.

This application is a national stage application under 35 U.S.C. 371 ofinternational application no. PCT/EP03/00407 filed Jan. 16, 2003, whichis based on German Application no. DE 102 01 783.2, filed on Jan. 17,2002, and claims priority thereto.

BACKGROUND OF THE INVENTION

The invention relates to a process for the oxidation of unsaturatedhydrocarbons, oxygen-containing hydrocarbons obtainable by this process,the liquid phase obtainable by this process, the oxygen-containinghydrocarbons obtainable by this process, chemical products comprisingthe oxygen-containing hydrocarbons, the use of these oxygen-containinghydrocarbons in chemical products, the use of acetic acid or of a saltof acetic acid in a process for the oxidation of unsaturatedhydrocarbons, a process for the preparation of water-soluble orwater-absorbent polymers, the water-soluble or water-absorbent polymersobtainable by this process, the use of a liquid phase for thepreparation of water-soluble or water-absorbent polymers, a composite, aprocess for the production of a composite, a composite obtainable bythis process, chemical products comprising the water-absorbent polymeror the composite, and the use of the water-absorbent polymer or of thecomposite in chemical products.

The oxidation of unsaturated hydrocarbons by atmospheric oxygen with theaid of heterogeneous or homogeneous catalysts is an industriallyimportant process. Thus, for example, by the catalytic oxidation ofpropylene by air, acetone and acrylic acid are obtained as productswhich are employed in the synthesis of many products prepared on a largeindustrial scale. Nevertheless, the oxidation of unsaturatedhydrocarbons by atmospheric oxygen as a rule leads to product mixtures.Thus, in the abovementioned oxidation of propylene by atmosphericoxygen, in addition to acetone and acrylic acid, other oxygen-containingproducts, for example acrolein, propionic acid, propionaldehyde, aceticacid, CO₂, acetaldehyde or methanol, are also obtained.

A number of processes have been described in the patent literature forthe oxidation of olefins on an industrial scale, both in the gas phaseand in the liquid phase. The selectivity of the oxidation of olefins byatmospheric oxygen depends above all on the reaction conditions and onthe catalyst systems employed.

In order preferentially to achieve an allylic oxidation of unsaturatedhydrocarbons, which in the case of propylene leads above all to acrylicacid as the main product, various processes and also various catalystsystems employed in these processes are described in the prior art.According to the current state of knowledge, of the noble metals Pdcatalysts are preferred in order, for example, to convert propylene asselectively as possible into acrylic acid with a good yield in solventsunder mild reaction conditions. Nevertheless, Pd catalysts also catalysevinylic oxidation of unsaturated hydrocarbons, which leads above all toketones, and in the case of propylene to acetone. The oxidation ofα-unsaturated hydrocarbons on Pd can be directed, however, in thedirection of an allylic oxidation by means of suitableelectron-withdrawing ligands and by the choice of particular solvents(LYONS J. E., SULD G., HUS Ch. Y., “Homogeneous Heterog. Catal. Proc.Int. Symp. Relat.”, Homogeneous Heterog. Catal., 5th (1986): 117-138;TROST B. M., METZNER P. J., J. Am. Chem. Soc., 102 (1980): 3572; KETELEYA. D., BRAATZ J., Chem. Comm. (1968): 169).

Reduced Pd catalyses the oxidation of propylene to acrylic acidparticularly selectively. For this, the reaction should be carried outwith an excess of propylene (O₂/C₃H₆<1). Reduction of the Pd catalystbefore the start of the reaction minimizes the formation of by-productsby vinylic oxidation to acetone and acetic acid already at the start ofoxidation (EP-A-145467, EP-A-145468 and EP-A-145469). Nevertheless, adisadvantage of the process described in these documents is the lowcatalyst output of a maximum of 0.038 g acrylic acid/g_(Pd)/hour.

In addition to allylic oxidation, however, it is also desirable todirect the oxidation of unsaturated hydrocarbons in the direction of avinylic oxidation. Acetone can be prepared from propylene in thismanner.

Industrially, acetone is prepared, for example, in co-production withphenol by oxidation of cumene or by dehydrogenation of isopropylalcohol. The process mentioned first has the disadvantage of astoichiometric production of a by-product (phenol), while in the oldersecond process the dehydrogenation does not proceed very efficiently. Inaddition to oxidation of cumene and dehydrogenation of isopropylalcohol, direct atmospheric oxidation of propylene via a 2-stage systemwith Pd(II) salts, Cu(II)Cl₂ and acetic acid (Wacker-Hoechst process) isalso of importance industrially. However, the disadvantage of thisprocess lies in the use of a mixture of metal ions as the catalyst, as aresult of which the separation and recovery of the noble metal palladiumis made very difficult. Furthermore, carrying out the reaction understrongly acid conditions necessitates the use of expensivecorrosion-resistant reactors. Another disadvantage of the Wacker-Hoechstprocess lies in the possible entrainment of residues of acid whenseparating off the organic product, necessitating additionalpurification steps.

BE 828603 discloses that the oxidation of propylene in the liquid phasecan be shifted in the direction of a vinylic oxidation to acetone ifother metal additives, for example heteropolyacids of molybdenum, suchas, for example, PMo₄V₈O₄₀ or TeMo₃V₃O₂₄, are added to the palladiumcatalyst. However, the experiments described in this document werecarried out at a pH of 1.0 and therefore require an acid-resistantreactor.

TROVOG B., MARES F. and DIAMOND S. (J. Am. Chem. Soc. 102 (1980): 6618)describe a process for the oxidation of propylene with molecular oxygento give acetone in diglyme as the solvent, in which cobalt-nitrocomplexes are employed as co-catalysts, together with Pd precursors. Thedisadvantage here also lies in the complicated separating off andrecovery of the noble metal palladium.

BRIEF SUMMARY OF THE PRESENT INVENTION

Generally, the object according to the invention is to overcome thedisadvantages resulting from the prior art.

The object according to the invention furthermore comprises providing aprocess in which unsaturated hydrocarbons can be subjected to selectiveallylic or vinylic oxidation by simple variation of the ligand.

Another object according to the invention comprised providing a processfor the oxidation of unsaturated hydrocarbons, preferably propylene,which converts propylene selectively into acrylic acid or acetone in aliquid phase under moderate conditions.

The invention is furthermore based on the object of providing a processfor the oxidation of propylene to acrylic acid in a liquid phase,wherein the liquid phase containing acrylic acid can subsequently beemployed for the preparation of polymers based on acrylic acid, withoutprior purification. By using the liquid phase containing acrylic acid inthe preparation of polymers, cost- and time-consuming concentrationsteps on the acrylic acid, such as are hitherto customary, can beavoided. This concentration of the acrylic acid is already uneconomicalbecause in the preparation of polymers by solution polymerization orinverse emulsion polymerization, the acrylic acid must in any case firstbe dissolved again in water.

DETAILED DESCRIPTION OF THE INVENTION

The above objects are achieved by a process for the oxidation ofunsaturated hydrocarbons, wherein an unsaturated hydrocarbon, anoxygen-containing oxidizing agent, a palladium complex as the catalystcontaining one, preferably two, ligands of the formula (I)

wherein R is a saturated, halogenated alkyl radical having from about 1to about 20 carbon atoms, preferably having up to about 10 carbon atoms,and particularly preferably having up to about 5 carbon atoms,and optionally auxiliary substances are brought into contact with oneanother in a liquid phase based on

-   (α1) from about 10 to about 100 vol. %, preferably from about 40 to    about 90 vol. % and particularly preferably from about 50 to about    75 vol. % of a protic polar solvent and-   (α2) from 0 to about 90 vol. %, preferably from about 10 to about 60    vol. % and particularly preferably from about 25 to about 50 vol. %    of an aprotic polar solvent, the sum of components (α1) and (α2)    being about 100 vol. %,    at a temperature in a range from about 30 to about 300° C.,    preferably in a range from about 45 to about 200° C. and    particularly preferably in a range from about 60 to about 120° C.,    under a pressure in a range from about 1 to about 200 bar,    preferably in a range from about 5 to about 150 bar and particularly    preferably in a range from about 10 to about 80 bar, such that,    preferably, as a result of which a liquid phase containing    oxygen-containing hydrocarbons is obtained.

In a particular embodiment of the process according to the invention, amixture based on

-   (α1) a protic polar solvent and-   (α2) an aprotic polar solvent, the weight ratio of the protic to the    aprotic solvent being in a range from about 100,000:1 to about 1:10,    particularly preferably in a range from about 1,000:1 to about 1:10    and more preferably in a range from about 10:1 to about 1:10,    is employed as the liquid phase.

Unsaturated hydrocarbons which are employed in the process according tothe invention are preferably olefins having from about 2 to about 60carbon atoms, which can be unbranched or branched, mono- orpolyunsaturated and optionally substituted, and can be described by theformula (II)

wherein R¹, R², R³ and R⁴ independently of one another can be hydrogen,an optionally branched C₁-C₈-alkyl, a straight-chain or branchedC₁-C₈-alkenyl, a phenyl radical or naphthyl radical, or wherein two ofthe radicals R¹ to R⁴ together can form an alkylene chain —(CH₂)_(m)—,wherein m=about 3 to about 10, preferably about 4 to about 9 andparticularly preferably about 5 to about 8, with the condition that atleast one of the radicals R¹ to R⁴ is either a hydrogen or a methylgroup. Particularly preferred unsaturated hydrocarbons which areemployed in the process according to the invention are chosen from thegroup consisting of propylene, isobutene, n-hexene, hexadienes, inparticular 1,5-hexadiene, n-octene, decene, dodecene, 1,9-decadiene,2-methyl-1-butene, 2,3-dimethyl-2-butene, 2-methyl-1-hexene,1,3-butadiene, 3-methyl-1,3-butadiene, octadecene, 2-ethyl-1-butene,styrene, cyclopentene, cyclohexene, 1-methyl-1-cyclohexene,cycloheptene, cyclooctene, cyclooctadiene, cyclododecene,cyclododecatriene, cyclohexadecadiene or limonene, propylene beingparticularly preferred.

Oxygen-containing oxidizing agents which are employed in the processaccording to the invention are preferably oxidizing agents which arecapable of transferring at least one oxygen atom to the hydrocarbonunder the reaction conditions described. Preferred oxygen-containingoxidizing agents are molecular oxygen (O₂), hydrogen peroxide (H₂O₂) anddinitrogen monoxide (N₂O), O₂ being particularly preferred. If O₂ isemployed as the oxidizing agent, it is furthermore preferable for theoxygen to be employed as a mixture with one or more inert gases, such asnitrogen, argon or CO₂, or in the form of air.

The halogenated radical R in the ligand of the palladium compound of theformula (I) is preferably a fluorinated branched or unbranched alkylradical, particularly preferably a branched or unbranched perfluoroalkylradical having from about 1 to 10 carbon atoms, for examplepentafluoroethyl or trifluoromethyl. A radical R which is particularlypreferred in this connection is the trifluoromethyl group (—CF₃).

The palladium complexes are prepared in the manner known to the expert,for example by reaction of a salt of an anion of the formula (I) with apalladium salt, preferably with PdCl₂, in aqueous solution. Pd(CF₃)₂ iscommercially obtainable, for example from ACROS, Belgium.

In a preferred embodiment of the process according to the invention, nofurther transition metals of sub-group VIII apart from palladium, andpreferably no transition metals, are employed.

In another preferred embodiment of the process according to theinvention, the palladium complex contains, in addition to the ligand ofthe formula (I), an organic ligand (X∩Y) which contains at least twoatoms X and Y of main group III, V or VI of the periodic table, whereinthis ligand can be coordinated to palladium via at least one of the twoatoms X and Y an wherein at least one of these atoms is a constituent ofa heterocyclic, aromatic ring system. The two atoms X and Y here can beidentical or different. The selectivity of the oxidation of unsaturatedhydrocarbons is shifted to the formation of ketones by the use of thisligand.

In a preferred embodiment of the organic ligand (X∩Y), this can becoordinated to palladium as a bidentate ligand via the two atoms X andY.

A particularly preferred ligand (X∩Y) which can be coordinated to thepalladium in addition to the ligand of the formula (I) is an organicligand which contains from about 5 to about 50, preferably from about 10to about 26 carbon atoms and at least two atoms from the following maingroups or combinations of main groups of the periodic table: III andIII, V and V, VI and VI, III and V, III and VI, V and VI, thecombination V and V being particularly preferred. Each of the maingroups or combinations of main groups of the periodic table hererepresents a preferred embodiment of a ligand (X∩Y) bonded to thepalladium complex.

It is furthermore preferable for the ligand (X∩Y), which can becoordinated to the palladium in addition to the ligand of the formula(I), to have at least the following structural element (III) withconjugated double bonds:

wherein at least two of the radicals Z¹ to Z⁴, preferably Z¹ and Z², Z¹and Z³, Z¹ and Z⁴, Z² and Z³, Z² and Z⁴ and Z³ and Z⁴, where Z¹ and Z²,Z² and Z³ and Z³ and Z⁴ are particularly preferred, are bonded to oneanother to form an aromatic ring system, preferably having from about 8to about 30, particularly preferably from about 8 to about 26 carbonatoms, and preferably from about 2 to about 8, particularly preferablyfrom about 2 to about 5 rings.

Ligands which are particularly preferred in this connection are chosenfrom the group consisting of 2,2′-bipyridyl (1), o-phenanthroline (2),bathophen-sulfonate (3), bathocuproin (4), 2,2′-biquinoyl (5),3,6-di-(2-pyridyl)-1,2,4,5-tetrazine (6), 2,2′-bipyrimidine (7) and2,3-di-(2-pyridyl)-pyrazine (8), where 2,2′-bipyridyl (1) andbathophen-sulfonate (3) are particularly preferred. In addition to this,it is preferable for the SO₃ ⁻ groups in the compound (3) to be in thepara-position.

If a palladium complex containing ligands of the formula (I) is employedas the catalyst, salts, co-catalysts, further co-ligands or promoterscan be employed as auxiliary substances in the process according to theinvention. This applies in particular if a palladium complex containingligands of the formula (I) but no organic ligands (X∩Y) is employed asthe catalyst. Salts which are preferably employed here are KClO₄, NaCl,Cs₂CO₃, Na(CH₃COO) or Na(CF₃COO). Preferred co-catalysts are metaladditives, for example Cu(BF₄)₂, Ag(CF₃COO), Co(salen), SnSO₄,Fe(acac)₃, Mo(acac)₃, MoO₂(acac)₂, K₂Cr₂O₇, Mn(CH₃COO)₃, Co(CH₃COO)₂, orNi(CF₃COO)₂. Preferred co-ligands are 18-crown-6,15-crown-5,hexafluoroacetylacetonate, trifluoroacetylacetonate or acetylacetonate.Promoters which are preferably employed are methyl iodide or freeradical initiators, such as N-hydroxy-phthalimide (NHPI).

The co-ligands and palladium are preferably employed in the processaccording to the invention in a molar ratio of co-ligand:palladium in arange from about 20:1 to about 4:1, particularly preferably in a molarratio in a range from about 12:1 to about 8:1. The salts are preferablyemployed in the process according to the invention in a concentration ina range from about 0.1 to about 10 mmol/l, particularly preferably in arange from about 0.5 to about 5 mmol/l. The promoters are preferablypresent in the process according to the invention in a concentration ina range from about 0.1 to about 10 mmol/l, particularly preferably in arange from about 0.5 to about 1 mmol/l. The co-catalysts are preferablyemployed in the process according to the invention in an amount suchthat the molar ratio between the metal of the co-catalyst and thepalladium is in a range from about 0.5:1 to about 2:1, preferably in arange from about 0.9:1 to about 1.1:1.

If a palladium complex containing ligands of the formula (I) but nofurther organic ligands (X∩Y) is employed as the catalyst, in apreferred embodiment of the process according to the invention aceticacid or a salt of acetic acid is employed as an auxiliary substance. Thesodium salt and the potassium salt and mixtures thereof are preferred asthe salt of acetic acid, the sodium salt being particularly preferred.It is furthermore preferable in this connection for the acetic acid orthe salt of acetic acid to be employed in an amount such that theCH₃COO— group is present in the liquid phase in protonated ornon-protonated form in a concentration in a range from about 0.001 toabout 100 mmol/l, preferably in a range from about 0.01 to about 50mmol/l and particularly preferably in a range from about 0.1 to about 10mmol/l.

Water, methanol and ethanol, acetic acid, trifluoroacetic acid andmixtures of at lest two of these are preferably employed as the proticpolar solvent in the process according to the invention, water andmixtures of water and trifluoroacetic acid in a weight ratio ofwater/trifluoroacetic acid in a range from about 10:1 to about 1:1,preferably from about 5:1 to about 3:1, being particularly preferred.

Aprotic polar solvents which are preferably employed are polyethyleneglycol dialkyl ethers, polyethylene glycol divinyl ethers orpolyethylene glycol vinyl alkyl ethers. Diethylene glycol dimethylether, triethylene glycol dimethyl ether, diethylene glycol methyl vinylether, triethylene glycol methyl vinyl ether, diethylene glycol divinylether, triethylene glycol divinyl ether, triethylene glycol diethylether, diethylene glycol diethyl ether and dimethylpropyleneurea (DMPU)are preferred among these, diethylene glycol dimethyl ether (diglyme)being particularly preferred.

In a particularly preferred embodiment of the process according to theinvention, a mixture of water and diglyme is employed as the liquidphase. In this connection it is preferable for the water and diglyme tobe employed in the liquid phase in a weight ratio of water:diglyme in arange from about 100,000:1 to about 1:10, particularly preferably in arange from about 1,000:1 to about 1:10 and more preferably in a rangefrom about 10:1 to about 1:10.

The pH of the liquid phase is preferably in a range from 0 to about 12,particularly preferably in a range from about 1 to about 11 and morepreferably in a range from about 2 to about 10.

The unsaturated hydrocarbon, the oxygen-containing oxidizing agent, thepalladium complex and optionally the auxiliary substances are preferablybrought into contact by first dissolving the catalyst, optionally withthe auxiliary substances, in the liquid phase. If the catalyst containsthe organic ligand (X∩Y) in addition to a ligand of the formula (I),before being brought into contact with the unsaturated hydrocarbon andthe oxygen-containing oxidizing agent the palladium complex is preparedby reaction of a palladium compound of the formula (III)

wherein the radical R′ has the same meaning as the radical R describedabove, with the organic ligand (X∩Y) in a molar ratio in a range fromabout 1:5 to about 5:1, preferably in a range from about 1:2 to about2:1, and particularly preferably in a molar ratio of about 1:1. Thereaction is preferably carried out at a temperature in a range fromabout 20 to about 80° C. under a pressure in a range from about 1 toabout 20 bar. In this connection, it is furthermore preferable for thepreparation of the palladium complexes to be carried out in situ. It isalso possible for this palladium complex to be prepared in a separatebatch by reaction of the palladium compound with the organic ligand inthe liquid phase and for the palladium complex prepared in this mannerthen to be transferred into the reaction vessel in which the oxidationof the unsaturated hydrocarbon takes place. The liquid phase in whichthe palladium complex is prepared preferably corresponds here in itschemical composition to the liquid phase in which the oxidation of theunsaturated hydrocarbon takes place. In this connection it isfurthermore preferable for the abovementioned palladium compound to bereacted with a mixture comprising at least two structurally differentorganic ligands (X∩Y) for the preparation of a palladium complex.

In another preferred embodiment of the process according to theinvention, the palladium complex is immobilized on a support and thesupport with the immobilized palladium complex is then introduced intothe liquid phase. Supports which are preferably employed are aluminiumhydroxide, silica gel, aluminium oxide, aluminium silicate, pumice,zeolites, tin oxides, preferably SnO₂, titanium oxides, preferably TiO₂,or active charcoal. The palladium complex is preferably immobilized byimmersing the support in a solution containing the palladium complex orby impregnating the support with a solution containing the palladiumcomplex at a temperature in a range from about 20 to about 150° C. undera pressure in a range from about 5 to about 100 bar. It is furthermorepossible to bond the catalyst chemically to a support via suitablefunctional groups on one of the ligands.

In a preferred embodiment of the process according to the invention, thepalladium complex is present in the liquid phase in a concentration in arange from about 0.001 to about 100 mmol/l, preferably in a range fromabout 0.01 to about 10 mmol/l and particularly preferably in a rangefrom about 0.1 to about 1 mmol/l.

If the oxygen-containing oxidizing agent is H₂O₂, this is added to theliquid phase together with the catalyst or the catalyst immobilized on asupport. If the oxygen-containing oxidizing agent is gaseous, this isbrought into contact, together with the unsaturated hydrocarbon underpressure, with the liquid phase containing the palladium complex andoptionally the auxiliary substances, preferably with vigorous stirringof the liquid phase, and the mixture is heated to the appropriatereaction temperature. On a large industrial scale, the liquid phase canbe brought into contact with the gaseous oxygen-containing oxidizingagent, for example, in a trickle bed with a bubble phase. In all cases,the liquid phase must be brought into contact with the oxygen-containingoxidizing agent in a manner such that the unsaturated hydrocarbon isoxidized by the oxygen-containing oxidizing agent to form anoxygen-containing hydrocarbon.

In a preferred embodiment of the process according to the invention, thepalladium complex is first activated by reduction, preferably toincrease the selectivity of the oxidation reaction, before it catalysesthe oxidation of the unsaturated hydrocarbon. In a preferred embodimentthe reduction of the palladium complex is carried out by hydrogen gas.For this, the hydrogen gas is brought into contact, before the oxidizingagent and preferably under a pressure in a range from about 1 to about20 bar at a temperature in a range from about 20 to about 80° C. in apressure vessel and while stirring, with the palladium complex, which ispreferably dissolved or dispersed in the aqueous phase.

In another preferred embodiment, the reduction of the palladium complexis effected by the unsaturated hydrocarbon. For this purpose, this isemployed with the oxidizing agent in the process according to theinvention in a molar ratio of unsaturated hydrocarbon/oxidizing agent ofat least about 1, preferably at least about 2 and particularlypreferably at least about 3. Reduction of the Pd catalyst with theunsaturated hydrocarbon before the start of the reaction minimizes thevinylic oxidation to the ketone already at the start of the reaction.

The period during which the unsaturated hydrocarbon, theoxygen-containing oxidizing agent and the palladium complex are broughtinto contact under the conditions described above depends on theindividual process parameters, in particular on the amounts of e-ductsemployed. However, the reaction is carried out under the statedconditions at least until a sufficient amount of the unsaturatedhydrocarbon employed, preferably at least about 10%, particularlypreferably at least about 20% and more preferably at least about 70% isconverted, that is to say has been oxidized by the oxidizing agent, theextent of the conversion being determined by the test method describedherein. In a preferred embodiment of the process according to theinvention, the individual components are brought into contact under theprocess conditions for at least about one hour, particularly preferablyfor at least about 2 hours. The reaction is preferably ended by endingthe contact of the unsaturated hydrocarbon with the palladium compoundin the liquid phase under the abovementioned pressure, preferably bypressure compensation between the reaction vessel and the surroundingatmosphere.

If a palladium complex which contains ligands of the formula (I) but nofurther organic ligands (X∩Y) is employed as the catalyst in the processaccording to the invention, the corresponding α,β-unsaturated carboxylicacid is obtained as the reaction product to an increased extent,preferably with a selectivity, determined in accordance with the methoddescribed herein, in a range from about 10 to about 99%, particularlypreferably in a range from about 20 to about 75% and more preferably ina range from about 29 to about 53%, provided that at least one of theradicals R¹ to R⁴ corresponds to a methyl group. In the case ofpropylene, if such a palladium complex is used acrylic acid isaccordingly obtained with a high selectivity, preferably in a range fromabout 10 to about 99%, particularly preferably in a range from about 20to about 75% and more preferably in a range from about 29 to about 53%.In this connection it is furthermore preferable for the value of thespecific catalyst output (═SCO value), determined in accordance with themethods described herein, for the synthesis of the α,β-unsaturatedcarboxylic acid from the corresponding unsaturated hydrocarbon,preferably for the synthesis of acrylic acid from propylene, to be atleast about 1 g/g_(Pd)/h, particularly preferably at least about 100g/g_(Pd)/h and more preferably at least about 1,000 g/g_(Pd)/h, where anSCO value of about 10,000 g/g_(Pd)/h is preferably not exceeded.

If a palladium complex which contains both a ligand of the formula (I)and the organic ligand (X∩Y) as ligands is employed as the catalyst inthe process according to the invention, the corresponding carbonylcompound is obtained as the reaction product to an increased extent,preferably with a selectivity, determined in accordance with the methoddescribed herein, in a range from about 60 to about 90%, preferably in arange from about 65 to about 85% and particularly preferably in a rangefrom about 70 to about 80%, provided that at least one of the radicalsR¹ to R⁴ corresponds to a hydrogen atom. In the case of propylene, ifsuch a palladium complex is used acetone is accordingly obtained with ahigh selectivity, preferably in a range from about 60 to about 90%,preferably in a range from about 65 to about 85% and particularlypreferably in a range from about 70 to about 80%. In this connection itis furthermore preferable for the SCO value, determined in accordancewith the methods described herein, for the synthesis of the carbonylcompound from the corresponding unsaturated hydrocarbon, preferably forthe synthesis of acetone from propylene, to be at least about 1g/g_(Pd)/h, particularly preferably at least about 100 g/g_(Pd)/h andmore preferably at least about 1,000 g/g_(Pd)/h, where an SCO value ofabout 10,000 g/g_(Pd)/h is preferably not exceeded.

The invention furthermore relates to the oxidized hydrocarbonsobtainable by the process according to the invention.

The invention also relates to the liquid phase obtainable by the processaccording to the invention containing oxidized hydrocarbons.

The invention also relates to the use of the oxidized hydrocarbonsobtainable by the process according to the invention in chemicalproducts, preferably in fibres, films and water-absorbent polymerstructures, which are preferably employed in the production of hygienearticles, such as diapers and other incontinence products, as well assanitary towels.

The invention moreover relates to chemical products comprising theoxidized hydrocarbons obtainable by the process according to theinvention, the abovementioned chemical products being preferred as thechemical products.

The invention moreover relates to the reduced palladium complexesdescribed above and the use thereof for the oxidation of unsaturatedhydrocarbons in the liquid phase.

The invention also relates to the use of acetic acid or of a salt ofacetic acid in the process according to the invention, wherein apalladium complex containing a ligand of the formula (I) but no furtherorganic ligands (X∩Y) is employed as the catalyst,

-   (δ1) to increase the SCO value of the palladium complex in the    oxidation of unsaturated hydrocarbons, preferably in the oxidation    of propylene, or-   (δ2) to increase the selectivity of the oxidation of unsaturated    hydrocarbons, preferably of propylene.

Preferred embodiments of the use according to the invention of aceticacid or of the salt of acetic acid result from the following uses orcombinations of uses: δ1, δ2, δ1δ2.

Preferred salts of acetic acid and ligands of the formula (I) are thosecompounds which have already been described in connection with theprocess according to the invention for the oxidation of unsaturatedhydrocarbons. The palladium complex is preferably prepared in the mannersuch as has been described in connection with the process according tothe invention for the oxidation of unsaturated hydrocarbons.

Preferably, increasing the SCO value (δ1) is understood as increasingthe SCO value compared with the SCO value of the oxidation of anunsaturated hydrocarbon with the same palladium complex but in theabsence of acetic acid or the salt of acetic acid. In this connection itis furthermore preferable for the increase in the SCO value to be atleast about 20%, preferably at least about 30%, in each case based onthe SCO value in the absence of acetic acid or the salt of acetic acid.

Increasing the selectivity (δ2) is preferably understood as increasingthe selectivity compared with the selectivity of the oxidation of anunsaturated hydrocarbon with the same palladium complex but in theabsence of acetic acid or the salt of acetic acid, with the sameconversion, that is to say at the same conversion of the unsaturatedhydrocarbon. In this connection it is furthermore preferable for theincrease in the selectivity to be at least about 50%, preferably atleast about 100%, in each case based on the selectivity in the absenceof acetic acid or the salt of acetic acid.

The invention also relates to a process for the preparation ofwater-soluble or water-absorbent polymers, wherein, in a liquid phaseobtainable by the process according to the invention for the oxidationof unsaturated hydrocarbons in which a palladium complex containingligands of the formula (I) but preferably no further organic ligands(X∩Y) is employed as the catalyst, the α,β-unsaturated carboxylic acidcontained as the oxygen-containing hydrocarbon in the liquid phase ispolymerized and the water-soluble or water-absorbent polymer obtained inthis way is then optionally dried and comminuted.

In a preferred embodiment of the process according to the invention forthe preparation of water-soluble or water-absorbent polymers, thatliquid phase which is obtainable by the process according to theinvention for the oxidation of unsaturated hydrocarbons in which wateror a mixture of water and diglyme, preferably in a weight ratio ofwater: diglyme in a range from about 10,000:1 to about 100:1, isemployed as the liquid phase and propylene is employed as theunsaturated hydrocarbon is employed as the liquid phase. The liquidphase is accordingly preferably an aqueous acrylic acid solution.

Preferred ligands of the formula (I) are those compounds which havealready been described in connection with the process according to theinvention for the oxidation of unsaturated hydrocarbons. The palladiumcomplex containing ligands of the formula (I) is preferably prepared ina manner such as has been described in connection with the processaccording to the invention for the oxidation of unsaturatedhydrocarbons.

It is furthermore preferable in the process according to the inventionfor the preparation of water-soluble or water-absorbent polymers for theα,β-unsaturated carboxylic acid contained in the liquid phase to becopolymerized with further monomers which can be copolymerized with theα,β-unsaturated carboxylic acid. These monomers are preferably compoundschosen from the group consisting of (β1) ethylenically unsaturatedmonomers containing acid groups or salts thereof or polymerized,ethylenically unsaturated monomers containing a protonated orquaternized nitrogen, or mixtures thereof, (β2) ethylenicallyunsaturated monomers which can be copolymerized with (β1), and (β3)crosslinking agents.

The ethylenically unsaturated monomers (β1) containing acid groups andthe α,β-unsaturated carboxylic acid contained in the liquid phaseobtainable by the process according to the invention for the oxidationof unsaturated hydrocarbons can be partly or completely, preferablypartly, neutralised. Preferably, the monoethylenically unsaturatedmonomers (β1) containing acid groups and the α,β-unsaturated carboxylicacid are neutralized to the extent of at least about 25 mol %,particularly preferably to the extent of at least about 50 mol % andmore preferably to the extent of about 50- about 90 mol %. Theneutralization of the monomers (β1) and of the α,β-unsaturatedcarboxylic acid can be carried out before and also after thepolymerization. Furthermore, the neutralization can be carried out withalkali metal hydroxides, alkaline earth metal hydroxides, ammonia andcarbonates and bicarbonates. In addition, any further base which forms awater-soluble salt with the acid is conceivable. Mixed neutralizationwith various bases is also conceivable. Neutralization with ammonia orwith alkali metal hydroxides is preferred, particularly preferably withsodium hydroxide or with ammonia.

Preferred monoethylenically unsaturated monomers (β1) containing acidgroups which can be employed alongside the α,β-unsaturated carboxylicacid contained in the liquid phase obtainable by the process accordingto the invention for the oxidation of unsaturated hydrocarbons areacrylic acid, methacrylic acid, ethacrylic acid, α-chloroacrylic acid,α-cyanoacrylic acid, β-methylacrylic acid (crotonic acid),α-phenylacrylic acid, β-acryloxypropionic acid, sorbic acid,α-chlorosorbic acid, 2′-methylisocrotonic acid, cinnamic acid,p-chlorocinnamic acid, β-stearyl acid, itaconic acid, citraconic acid,mesaconic acid, glutaconic acid, aconitic acid, maleic acid, fumaricacid, tricarboxyethylene and maleic anhydride, where acrylic acid andmethacrylic acid are particularly preferred.

In addition to these monomers containing carboxylate groups,ethylenically unsaturated sulfonic acid monomers or ethylenicallyunsaturated phosphonic acid monomers are furthermore preferred asmonoethylenically unsaturated monomers (β1) containing acid groups.

Preferred ethylenically unsaturated sulfonic acid monomers areallylsulfonic acid or aliphatic or aromatic vinylsulfonic acids oracrylic or methacrylic sulfonic acids. Preferred aliphatic or aromaticvinylsulfonic acids are vinylsulfonic acid, 4-vinylbenzenesulfonic acid,vinyltoluenesulfonic acid and styrenesulfonic acid. Preferred acrylo- ormethacrylosulfonic acids are sulfoethyl (meth)acrylate, sulfopropyl(meth)acrylate and 2-hydroxy-3-methacryloxypropylsulfonic acid.2-Acrylamido-2-methylpropanesulfonic acid is the preferred(meth)acrylamidoalkylsulfonic acid.

Ethylenically unsaturated phosphonic acid monomers, such asvinylphosphonic acid, allylphosphonic acid, vinylbenzylphosphonic acid,(meth)acrylamidoalkylphosphonic acids, acrylamidoalkyldiphosphonicacids, phosphonomethylated vinylamines and (meth)acrylophosphonic acidderivatives, are furthermore preferred.

Preferred ethylenically unsaturated monomers (β1) containing aprotonated nitrogen are, preferably, dialkylaminoalkyl (meth)acrylatesin protonated form, for example dimethylaminoethyl (meth)acrylatehydrochloride or dimethylaminoethyl (meth)acrylate hydrosulfate, anddialkylaminoalkyl-(meth)acrylamides in protonated form, for exampledimethylaminoethyl(meth)acrylamide hydrochloride,dimethylaminopropyl(meth)acrylamide hydrochloride,dimethylaminopropyl(meth)acrylamide hydrosulfate ordimethylaminoethyl(meth)acrylamide hydrosulfate.

Preferred ethylenically unsaturated monomers (β1) containing aquaternized nitrogen are dialkylammoniumalkyl (meth)acrylates inquaternized form, for example trimethylammoniumethyl (meth)acrylatemethosulfate or dimethylethylammoniumethyl (meth)acrylate ethosulfate,and (meth)acrylamidoalkyldialkylamines in quaternized form, for example(meth)acrylamidopropyltrimethylammonium chloride, trimethylammoniumethyl(meth)acrylate chloride or (meth)acrylamidopropyltrimethylammoniumsulfate.

Preferred monoethylenically unsaturated monomers (β2) which can becopolymerized with (β1) are acrylamides and methacrylamides.

Possible (meth)acrylamides are, in addition to acrylamide andmethacrylamide, alkyl-substituted (meth)acrylamides oraminoalkyl-substituted derivatives of (meth)acrylamide, such asN-methylol(meth)acrylamide, N,N-dimethylamino(meth)acrylamide,dimethyl(meth)acrylamide or diethyl(meth)acrylamide. Possiblevinylamides are, for example, N-vinylamides, N-vinylformamides,N-vinylacetamides, N-vinyl-N-methylacetamides,N-vinyl-N-methylformamides, vinylpyrrolidone. Among these monomers,acrylamide is particularly preferred.

Water-dispersible monomers are furthermore preferred asmonoethylenically unsaturated monomers (β2) which can be copolymerizedwith (β1). Preferred water-dispersible monomers are acrylic acid estersand methacrylic acid esters, such as methyl (meth)acrylate, ethyl(meth)acrylate, propyl (methyl)acrylate or butyl (meth)acrylate, as wellas vinyl acetate, styrene and isobutylene.

Crosslinking agents (β3) which are preferred according to the inventionare compounds which contain at least two ethylenically unsaturatedgroups within a molecule (crosslinking agent class I), compounds whichcontain at least two functional groups which can react with functionalgroups of monomers (β1) or (β2) in a condensation reaction(=condensation-crosslinking agents), in an addition reaction or in aring-opening reaction (crosslinking agent class II), compounds whichcontain at least one ethylenically unsaturated group and at least onefunctional group which can react with functional groups of monomers (β1)or (β2) in a condensation reaction, in an addition reaction or in aring-opening reaction (crosslinking agent class III), or polyvalentmetal cations (crosslinking agent class IV). A crosslinking of thepolymers by free-radical polymerization of the ethylenically unsaturatedgroups of the crosslinking agent molecule with the monoethylenicallyunsaturated monomers (β1) or (β2) is achieved here by the compounds ofcrosslinking agent class I, while in the case of the compounds ofcrosslinking agent class II and the polyvalent metal cations ofcrosslinking agent class IV crosslinking of the polymers is achieved bya condensation reaction of the functional groups (crosslinking agentclass II) or by electrostatic interaction of the polyvalent metal cation(crosslinking agent class IV) with the functional groups of monomers(β1) or (β2). In the case of the compounds of crosslinking agent classIII crosslinking of the polymer accordingly takes place both byfree-radical polymerization of the ethylenically unsaturated group andby a condensation reaction between the functional group of thecrosslinking agent and the functional groups of monomers (β1) or (β2).

Preferred compounds of crosslinking agent class I are poly(meth)acrylicacid esters, which are obtained, for example, by reaction of a polyol,such as, for example, ethylene glycol, propylene glycol,trimethylolpropane, 1,6-hexanediol, glycerol, pentaerythritol,polyethylene glycol or polypropylene glycol, an amino alcohol, apolyalkylene-polyamine, such as, for example, diethylenetriamine ortriethylenetetramine, or an alkoxylated polyol with acrylic acid ormethacrylic acid. Preferred compounds of crosslinking agent class I arefurthermore polyvinyl compounds, poly(meth)allyl compounds,(meth)acrylic acid esters of a monovinyl compound or (meth)acrylic acidesters of a mono(meth)allyl compound, preferably of the mono(meth)allylcompounds of a polyol or of an amino alcohol.

Examples of compounds of crosslinking agent class I which may bementioned are alkenyl di(meth)acrylates, for example ethylene glycoldi(meth)acrylate, 1,3-propylene glycol di(meth)acrylate, 1,4-butyleneglycol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate,1,6-hexanediol di(meth)acrylate, 1,10-decanediol di(meth)acrylate,1,12-dodecanediol di(meth)acrylate, 1,18-octadecanedioldi(meth)acrylate, cyclopentanediol di(meth)acrylate, neopentylglycoldi(meth)acrylate, methylene di(meth)acrylate or pentaerythritoldi(meth)acrylate, alkenyldi(meth)acrylamides, for exampleN-methyldi(meth)acrylamide, N,N′-3-methylbutylidenebis(meth)acrylamide,N,N′-(1,2-dihydroxyethylene)bis(meth)acrylamide,N,N′-hexamethylenebis(meth)acrylamide orN,N′-methylenebis(meth)acrylamide, polyalkoxy-di(meth)acrylates, forexample diethylene glycol di(meth)acrylate, triethylene glycoldi(meth)acrylate, tetraethylene glycol di(meth)acrylate, dipropyleneglycol di(meth)acrylate, tripropylene glycol di(meth)acrylate ortetrapropylene glycol di(meth)acrylate, bisphenol A di(meth)acrylate,ethoxylated bisphenol A di(meth)acrylate, benzylidene di(meth)acrylate,1,3-di(meth)acryloyloxy-propan-2-ol, hydroquinone di(meth)acrylate,di(meth)acrylate esters of trimethylolpropane oxyalkylated, preferablyethoxylated, preferably with from about 1 to about 30 mol of alkyleneoxide per hydroxyl group, thioethylene glycol di(meth)acrylate,thiopropylene glycol di(meth)acrylate, thiopolyethylene glycoldi(meth)acrylate, thiopolypropylene glycol di(meth)acrylate, divinylethers, for example 1,4-butanediol-divinyl ether, divinyl esters, forexample divinyl adipate, alkanedienes, for example butadiene or1,6-hexadiene, divinylbenzene, di(meth)allyl compounds, for exampledi(meth)allyl phthalate or di(meth)allyl succinate, homo- and copolymersof di(meth)allyldimethylammonium chloride and homo- and copolymers ofdiethyl (meth)allylaminomethyl(meth)acrylate-ammonium chloride,vinyl(meth)acrylyl compounds, for example vinyl (meth)acrylate,(meth)allyl-(meth)acrylyl compounds, for example (meth)allyl(meth)acrylate, (meth)allyl (meth)acrylate ethoxylated with from about 1to about 30 mol of ethylene oxide per hydroxyl group, di(meth)allylesters of polycarboxylic acids, for example di(meth)allyl maleate,di(meth)allyl fumarate, di(meth)allyl succinate or di(meth)allylterephthalate, compounds with 3 or more ethylenically unsaturated groupswhich can be polymerized by free radicals, such as, for example,glycerol tri(meth)acrylate, (meth)acrylate esters of glyceroloxyethylated with preferably from about 1 to about 30 mol of ethyleneoxide per hydroxyl group, trimethylolpropane tri(meth)acrylate,tri(meth)acrylate esters of trimethylolpropane oxyalkylated, preferablyethoxylated, preferably with from about 1 to about 30 ml of alkyleneoxide per hydroxyl group, trimethylacrylamide, (meth)allylidenedi(meth)acrylate, 3-allyloxy-1,2-propanediol di(meth)acrylate,tri(meth)allyl cyanurate, tri(meth)allyl isocyanurate, pentaerythritoltetra(meth)acrylate, pentaerythritol tri(meth)acrylate, (meth)acrylicacid esters of pentaerythritol oxyethylated with preferably 1 to 30 molof ethylene oxide per hydroxyl group, tris(2-hydroxyethyl) isocyanuratetri(meth)acrylate, trivinyl trimellitate, tri(meth)allylamine,di(meth)allylalkylamines, for example di(meth)allylmethylamine,tri(meth)allyl phosphate, tetra(meth)allylethylenediamine,poly(meth)allyl esters, tetra(meth)allyloxyethane ortetra(meth)allylammonium halides.

Compounds which contain at least two functional groups which can reactwith the functional groups of monomers (β1) or (β2), preferably withacid groups of monomers (β1), in a condensation reaction(=condensation-crosslinking agents), in an addition reaction or in aring-opening reaction are preferred as the compound of crosslinkingagent class II. These functional groups of compounds of crosslinkingagent class II are preferably alcohol, amine, aldehyde, -glycidyl,isocyanate, carbonate or epichloro functions.

Examples which may be mentioned of the compound of crosslinking agentclass II are polyols, for example ethylene glycol, polyethylene glycols,such as diethylene glycol, triethylene glycol and tetraethylene glycol,propylene glycol, polypropylene glycols, such as dipropylene glycol,tripropylene glycol or tetrapropylene glycol, 1,3-butanediol,1,4-butanediol, 1,5-pentanediol, 2,4-pentanediol, 1,6-hexanediol,2,5-hexanediol, glycerol, polyglycerol, trimethylolpropane,polyoxypropylene, oxyethylene/oxypropylene block copolymers, sorbitanfatty acid esters, polyoxyethylene sorbitan fatty acid esters,pentaerythritol, polyvinyl alcohol and sorbitol, amino alcohols, forexample ethanolamine, diethanolamine, triethanolamine or propanolamine,polyamine compounds, for example ethylenediamine, diethylenetriamine,triethylenetetraamine, tetraethylenepentaamine orpentaethylenehexaamine, polyglycidyl ether compounds, such as ethyleneglycol diglycidyl ether, polyethylene glycol diglycidyl ether, glyceroldiglycidyl ether, glycerol polyglycidyl ether, pentaerythritolpolyglycidyl ether, propylene glycol diglycidyl ether, polypropyleneglycol diglycidyl ether, neopentylglycol diglycidyl ether, hexanediolglycidyl ether, trimethylolpropane polyglycidyl ether, sorbitolpolyglycidyl ether, phthalic acid diglycidyl ester, adipic aciddiglycidyl ether, 1,4-phenylene-bis(2-oxazoline), glycidol,polyisocyanates, preferably diisocyanates, such as 2,4-toluenediisocyanate and hexamethylene diisocyanate, polyaziridine compounds,such as 2,2-bishydroxymethylbutanol tris[3-(1-aziridinyl)propionate],1,6-hexamethylenediethyleneurea anddiphenylmethane-bis-4,4′-N,N′-diethyleneurea, halogenoepoxides, forexample epichloro- and epibromohydrin and α-methylepichlorohydrin,alkylene carbonates, such as 1,3-dioxolan-2-one (ethylene carbonate),4-methyl-1,3-dioxolan-2-one (propylene carbonate),4,5-dimethyl-1,3-dioxolan-2-one, 4,4-dimethyl-1,3-dioxolan-2-one,4-ethyl-1,3-dioxolan-2-one, 4-hydroxymethyl-1,3-dioxolan-2-one,1,3-dioxan-2-one, 4-methyl-1,3-dioxan-2-one,4,6-dimethyl-1,3-dioxan-2-one, 1,3-dioxolan-2-one,poly-1,3-dioxolan-2-one and polyquaternary amines, such as condensationproducts of dimethylamines and epichlorohydrin. Preferred compounds ofcrosslinking agent class II are furthermore polyoxazolines, such as1,2-ethylenebisoxazoline, crosslinking agents with silane groups, suchas γ-glycidoxypropyltrimethoxysilane and γ-aminopropyltrimethoxysilane,oxazolidinones, such as 2-oxazolidinone, bis- and poly-2-oxazolidinonesand diglycol silicates.

Preferred compounds of class III are esters, containing hydroxyl oramino groups, of (meth)acrylic acid, such as, for example,2-hydroxyethyl (meth)acrylate, and (meth)acrylamides containing hydroxylor amino groups or mono(meth)allyl compounds of diols.

The polyvalent metal cations of crosslinking agent class IV arepreferably derived from mono- or polyvalent cations, and the monovalentin particular from alkali metals, such as potassium, sodium and lithium,lithium being preferred. Preferred divalent cations are derived fromzinc, beryllium and alkaline earth metals, such as magnesium, calciumand strontium, magnesium being preferred. Cations of higher valencywhich can furthermore be employed according to the invention are cationsof aluminium, iron, chromium, manganese, titanium, zirconium and othertransition metals, as well as double salts of such cations or mixturesof the salts mentioned. Aluminium salts and alums and various hydratesthereof, such as e.g. AlCl₃×6H₂O, NaAl(SO₄)₂×12H₂O, KAl(SO₄)₂×12H₂O orAl₂(SO₄)₃×14-18H₂O, are preferably employed.

Al₂(SO₄)₃ and its hydrates are particularly preferably used ascrosslinking agents of crosslinking agent class IV.

Crosslinking agents of the following crosslinking agent classes andcrosslinking agents of the following combinations of crosslinking agentclasses are preferably employed in the process according to theinvention for the preparation of water-soluble or water-absorbentpolymers: I, II, III, IV, I II, I III, I IV, I II III, I II IV, I IIIIV, II III IV, II IV or III IV.

Further preferred embodiments of the process according to the inventionare processes in which any desired one of the abovementionedcrosslinking agents of crosslinking agent class I is employed as thecrosslinking agent. Among these, water-soluble crosslinking agents arepreferred. In this connection, N,N′-methylenebisacrylamide, polyethyleneglycol di(meth)acrylates, triallylmethylammonium chloride,tetraallylammonium chloride and allyl-nonaethylene glycol acrylateprepared with about 9 mol of ethylene oxide per mol of acrylic acid areparticularly preferred.

The abovementioned monomers and crosslinking agents are added,optionally with further adjuvants (β4), before the polymerization of theliquid phase which is obtainable by the process according to theinvention for the oxidation of unsaturated hydrocarbons and contains theα,β-unsaturated carboxylic acid as oxygen-containing hydrocarbons.Preferred adjuvants (β4) in this connection are standardizing agents,odour-binding agents, surface-active agents or antioxidants. However,these adjuvants (β4) can also be added after the polymerization of theliquid phase or, after drying and comminution of the polymers, can bemixed with these. The water-soluble or water-absorbent polymer can beprepared by various polymerization procedures. In this connection theremay be mentioned as examples solution polymerization, spraypolymerization, inverse emulsion polymerization and inverse suspensionpolymerization. Solution polymerization is preferably carried out. Abroad spectrum of possible variations in respect of reactioncircumstances, such as temperatures, nature and amount of initiators andalso the reaction solution, can be found from the prior art. Typicalprocesses are described in the following patent specifications: U.S.Pat. No. 4,286,082, U.S. Pat. No. 4,179,367, U.S. Pat. No. 4,076,663,U.S. Pat. No. 4,587,308, U.S. Pat. No. 5,409,771, U.S. Pat. No.5,610,220, U.S. Pat. No. 5,672,633, U.S. Pat. No. 5,712,316.

Polymerization initiators can be contained in the liquid phase indissolved or dispersed form. Possible initiators are all the compoundsknown to the expert which dissociate into free radicals. These include,in particular, peroxides, hydroperoxides, hydrogen peroxide,persulfates, azo compounds and the so-called redox catalysts. The use ofwater-soluble catalysts is preferred. In some cases it is advantageousto use mixtures of various polymerization initiators. Among thesemixtures, those of hydrogen peroxide and sodium peroxodisulfate orpotassium peroxodisulfate, which can be employed in any conceivableratio of amounts, are preferred. Suitable organic peroxides are,preferably, acetylacetone peroxide, methyl ethyl ketone peroxide,t-butyl hydroperoxide, cumene hydroperoxide, t-amyl perpivalate, t-butylperpivalate, t-butyl pemeohexonate, t-butyl isobutyrate, t-butylper-2-ethylhexenoate, t-butyl perisononanoate, t-butyl permaleate,t-butyl perbenzoate, t-butyl 3,5,5-tri-methylhexanoate and amylperneodecanoate. Polymerization initiators which are furthermorepreferred are: azo compounds, such as 2,2′-azobis-(2-amidinopropane)dihydrochloride, azo-bis-amidinopropane dihydrochloride,2,2′-azobis-(N,N-dimethylene)isobutyramidine dihydrochloride,2-(carbamoylazo)isobutyronitrile and 4,4′-azobis-(4-cyanovaleric acid).The compounds mentioned are employed in conventional amounts, preferablyin a range from about 0.01 to about 5, preferably from about 0.1 toabout 2 mol %, in each case based on the amount of monomers to bepolymerized.

The redox catalysts contain as the oxidic component at least one of theabove-mentioned per-compounds and as the reducing component, preferably,ascorbic acid, glucose, sorbose, mannose, ammonium or alkali metalhydrogen sulfite, sulfate, thiosulfate, hyposulfite or sulfide, metalsalts, such as iron(II) ions or silver ions or sodiumhydroxymethyl-sulfoxylate. Ascorbic acid or sodium pyrosulfite ispreferably used as the reducing component of the redox catalyst. Fromabout 1*10⁻⁵ to about 1 mol % of the reducing component of the redoxcatalyst and from about 1*10⁻⁵ to about 5 mol % of the oxidizingcomponent of the redox catalyst are employed, based on the amount ofmonomers employed in the polymerization. Instead of the oxidizingcomponent of the redox catalysts, or in addition to this, one or more,preferably water-soluble azo compounds can be used.

A redox system comprising hydrogen peroxide, sodium peroxodisulfate andascorbic acid is preferably employed according to the invention.Generally, azo compounds are preferred according to the invention asinitiators, azo-bis-amidinopropane dihydrochloride being particularlypreferred. As a rule, the polymerization is initiated with theinitiators in a temperature range from about 30 to about 90° C.

Another possibility for the preparation according to the invention ofwater-absorbent polymers is first to prepare non-crosslinked, inparticular linear polymers, preferably by the free-radical route, fromthe α,β-unsaturated carboxylic acid and optionally the abovementionedmonoethylenically unsaturated monomers (β1) or (β2) and then to reactthese with reagents (β3) having a crosslinking action, preferably thoseof classes II and IV. This variant is preferably employed if thewater-absorbent polymers are first to be processed in shaping processes,for example to give fibres, films or other sheet-like structures, suchas woven fabrics, knitted fabrics, spun fabrics or nonwovens, and are tobe crosslinked in this form.

In another preferred embodiment of the process according to theinvention for the preparation of water-soluble or water-absorbentpolymers, in addition to the α,β-unsaturated carboxylic acid, preferablyacrylic acid, and optionally to the further monomers (β1), (β2) andcrosslinking agents (β3), water-soluble polymers (β5) are polymerizedin. These water-soluble polymers (β5) are preferably partly orcompletely hydrolysed polyvinyl alcohol, polyvinylpyrrolidone, starch orstarch derivatives, polyglycols or polyacrylic acid. The molecularweight of these polymers is not critical as long as they arewater-soluble. Preferred water-soluble polymers (β5) are starch orstarch derivatives or polyvinyl alcohol. The water-soluble polymers,preferably synthetic, such as polyvinyl alcohol, can also be used as agrafting base for the monomers to be polymerized. In another preferredembodiment of the process according to the invention, after drying andcomminution, the water-soluble or water-absorbent polymers are mixedwith the water-soluble polymers (β5) described above, it being possiblefor the mixing units known to the expert to be used for the mixing.

In a preferred embodiment of the process according to the invention, theα,β-unsaturated carboxylic acid contained in the liquid phase obtainableby the process according to the invention for the oxidation ofunsaturated hydrocarbons, the monomers (β1) and (β2), the crosslinkingagents (β3), the adjuvants (β4) and the water-soluble polymers (β5) areemployed in an amount such that the water-soluble or water-absorbentpolymer obtainable by the process is based on

-   (γ1) from about 0.1 to about 99.999 wt. %, preferably from about 20    to about 98.99 wt. % and particularly preferably from about 30 to    about 98.95 wt. % of monomers-   (γ1) or of the α,β-unsaturated carboxylic acid or mixtures thereof,-   (γ2) from 0 to about 70 wt. %, preferably from about 1 to about 60    wt. % and particularly preferably from about 1 to about 40 wt. % of    the monomers (β2),-   (γ3) from about 0.001 to about 10 wt. %, preferably from about 0.01    to about 7 wt. % and particularly preferably from about 0.05 to    about 5 wt. % of the crosslinking agents (β3),-   (γ4) from 0 to about 20 wt. %, preferably from about 0.01 to about 7    wt. % and particularly preferably from about 0.05 to about 5 wt. %    of the adjuvants (β4) and-   (γ4) from 0 to about 30 wt. %, preferably from about 1 to about 20    wt. % and particularly preferably from about 5 to about 10 wt. % of    the water-soluble polymers (β5), the sum of the amounts by weight    (γ1) to (γ5) being about 100 wt. %.

In another preferred embodiment of the process according to theinvention, the α,β-unsaturated carboxylic acid, the monomers (β1) and(β2), the crosslinking agents (β3), the adjuvants (β4) and thewater-soluble polymers (β5) are employed in an amount such that thewater-soluble or water-absorbent polymer comprises to the extent of atleast about 50 wt. %, preferably to the extent of at least about 70 wt.% and more preferably to the extent of at least about 90 wt. % monomerswhich contain carboxylate groups and are based to the extent of at leastabout 50 wt. %, preferably to the extent of at least about 70 wt. % andmore preferably to the extent of at least about 90 wt. %, based on thetotal weight of the monomers containing carboxylate groups, on thoseα,β-unsaturated carboxylic acids which were obtained before thepolymerization as oxidized hydrocarbons in the liquid phase obtainableby the process according to the invention for the oxidation ofunsaturated hydrocarbons. In this connection it is particularlypreferable for the water-soluble or water-absorbent polymer to compriseto the extent of at least about 50 wt. %, preferably to the extent of atleast about 70 wt. % acrylic acid which is based to the extent of atleast about 50 wt. %, preferably to the extent of at least about 70 wt.% and more preferably to the extent of at least about 90 wt. %, based onthe total weight of the acrylic acid, on that acrylic acid which wasobtained before the polymerization as the oxidized hydrocarbon in theliquid phase obtainable by the process according to the invention forthe oxidation of unsaturated hydrocarbons, the acrylic acid preferablybeing neutralized to the extent of at least about 20 mol %, particularlypreferably to the extent of at least about 50 mol %.

In another preferred embodiment of the process according to theinvention, the α,β-unsaturated carboxylic acid, the monomers (β1) and(β2), the crosslinking agents (β3), the adjuvants (β4) and thewater-soluble polymers (β5) are employed in an amount such that the freeacid groups predominate in the polymer formed, so that this polymer hasa pH which lies in the acidic range. These acidic water-absorbentpolymers can be at least partly neutralized by a polymer with free basicgroups, preferably amine groups, which is basic in comparison with theacidic polymer. These polymers are called “mixed-bed ion-exchangeabsorbent polymers” (MBIEA polymers) in the literature and aredisclosed, inter alia, in U.S. Pat. Nos. 6,380,456, 6,258,996, and6,232,520. As a rule, MBIEA polymers are a composition which compriseson the one hand basic polymers which are capable of exchanging anionsand on the other hand a polymer which is acidic compared with the basicpolymer and is capable of exchanging cations. The basic polymer containsbasic groups and is typically obtained by the polymerization of monomerswhich carry basic groups or groups which can be converted into basicgroups. These monomers are, above all, those which contain primary,secondary or tertiary amines or the corresponding phosphines or at leasttwo of the above functional groups. This group of monomers includes, inparticular, ethylene-amine, allylamine, diallylamine, 4-aminobutene,alkyloxycyclines, vinylformamide, 5-aminopentene, carbodiimide,formaldacin, melanine and the like, and secondary or tertiary aminederivatives thereof.

It is furthermore preferable for the liquid phase to contain theα,β-unsaturated carboxylic acid in an amount in a range from about 5 toabout 50 wt. %, preferably in a range from about 10 to about 40 wt. %and moreover preferably in a range from about 20 to about 30 wt. %, ineach case based on the total weight of the liquid phase. If the liquidphase obtainable by the process according to the invention for theoxidation of unsaturated hydrocarbons contains the α,β-unsaturatedcarboxylic acid in an amount which lies outside the range describedabove, the liquid phase can optionally be diluted by addition of wateror concentrated before the polymerization, the concentration preferablybeing carried out by distillation.

It is furthermore preferable in the process according to the inventionfor the preparation of water-soluble or water-absorbent polymers for thepalladium complex to be separated off from the liquid phase containingthe α,β-unsaturated carboxylic acids, which was obtained by the processaccording to the invention for the oxidation of unsaturatedhydrocarbons, before the polymerization. The palladium complex ispreferably separated off here by filtration of the liquid phase or bychromatographic purification steps, filtration of the liquid phase beingparticularly preferred.

In one embodiment of the process according to the invention for thepreparation of water-soluble or water-absorbent polymers, theα,β-unsaturated carboxylic acid contained in the liquid phase is notconcentrated before the polymerization. In another embodiment of theprocess according to the invention for the preparation of water-solubleor water-absorbent polymers, the liquid phase is employed in anuntreated form for the preparation according to the invention of thewater-soluble or water-absorbent polymers.

In another embodiment of the process according to the invention for thepreparation of water-soluble or water-absorbent polymers, the outerregion of the polymer is brought into contact with a crosslinking agent,after drying and comminution of the polymers, so that preferably as aresult of which the outer region has a higher degree of crosslinkingthan the inner region, so that a core-shell structure preferably forms.In this connection it is furthermore preferable for the inner region tohave a larger diameter than the outer region. Preferred crosslinkingagents (so-called after-crosslinking agents) here are the crosslinkingagents of crosslinking agent classes II and IV. Ethylene carbonate isparticularly preferred as the after-crosslinking agent.

The invention also relates to the water-soluble or water-absorbentpolymers obtainable by the process according to the invention for thepreparation of water-soluble or water-absorbent polymers.

In a preferred embodiment of the water-absorbent polymers, these have atleast one of the following properties

-   (A) maximum uptake of about 0.9 wt. % aqueous NaCl in accordance    with ERT 440.1-99 in a range from about 10 to about 1,000,    preferably from about 15 to about 500 and particularly preferably    from about 20 to about 300 ml/g,-   (B) the content extractable with about 0.9 wt. % aqueous NaCl    solution in accordance with ERT 470.1-99 is less than about 30,    preferably less than about 20 and particularly preferably less than    about 10 wt. %, based on the untreated absorbent polymer structures,    and-   (C) the swelling time to achieve about 80% of the maximum absorption    of about 0.9 wt. % aqueous NaCl in accordance with ERT 440.1-99 is    in the range from about 0.01 to about 180, preferably from about    0.01 to about 150 and particularly preferably from about 0.01 to    about 100 min,-   (D) the bulk density in accordance with ERT 460.1-99 is in the range    from about 300 to about 1,000, preferably from about 310 to about    800 and particularly preferably from about 320 to about 700 g/l,-   (E) the pH in accordance with ERT 400.1-99 of about 1 g of the    untreated absorbent polymer structure in 1 l of water is in the    range from about 4 to about 10, preferably from about 5 to about 9    and particularly preferably from about 5.5 to about 7.5,-   (F) CRC in accordance with ERT 441.1-99 in the range from about 10    to about 100, preferably from about 15 to about 80 and particularly    preferably from about 20 to about 60 g/g,-   (G) AAP in accordance with ERT 442.1-99 under a pressure of about    0.3 psi in the range from about 10 to about 60, preferably from    about 15 to about 50 and particularly preferably from about 20 to    about 40 g/g.

The combinations of properties of two or more of these propertiesresulting from the above properties are in each case preferredembodiments of the water-absorbent polymer according to the invention.Embodiments according to the invention which are particularly preferredare furthermore polymers which have the properties or combinations ofproperties shown below as letters or combinations of letters: A, B, C,D, E, F, G, AB, ABC, ABCD, ABCDE, ABCDEF, ABCDEFG, BC, BCD, BCDE, BCDEF,BCDEFG, CD, CDE, CDEF, CDEFG, DE, DEF, DEFG, EF, EFG, FG.

The invention also relates to the use of a liquid phase containing anα,β-unsaturated carboxylic acid, preferably an aqueous acrylic acidsolution, obtainable by the process according to the invention for theoxidation of unsaturated hydrocarbons, for the preparation ofwater-soluble or water-absorbent polymers.

The invention furthermore relates to the use of a composite comprising awater-absorbent polymer obtainable by the process according to theinvention for the preparation of water-absorbent polymers and asubstrate. It is preferable for the water-absorbent polymer and thesubstrate to be firmly bonded to one another. Preferred substrates arefilms of polymers, such as, for example, of polyethylene, polypropyleneor polyamide, metals, nonwovens, fluff, tissues, woven fabric, naturallyoccurring or synthetic fibres or other foams.

Sealing materials, cable, absorbent cores and diapers and hygienearticles containing these are preferred according to the invention asthe composite.

The sealing materials are, preferably, water-absorbent films, whereinthe water-absorbent polymer according to the invention is incorporatedinto a polymer matrix or fibre matrix as the substrate. This ispreferably carried out by mixing the water-absorbent polymer with apolymer (Pm) which forms the polymer matrix or fibre matrix and thenbonding them by heat treatment if appropriate. In the case where theabsorbent structure is employed as a fibre, yarns can be obtainedtherefrom, which are spun with further fibres made of another materialas the substrate and are then bonded to one another, for example byweaving or knitting, or are bonded directly, i.e. without being spunwith further fibres. Typical processes for this purpose are described inH. Savano et al., International Wire & Cabel Symposium Proceedings 40,333 to 338 (1991); M. Fukuma et al., International Wire & CabelSymposium Proceedings, 36, 350 to 355 (1987) and in U.S. Pat. No.4,703,132.

In the embodiment in which the composite is a cable, the water-absorbentpolymer according to the invention can be employed as particlesdirectly, preferably under the insulation of the cable. In anotherembodiment of the cable the water-absorbent polymer can be employed inthe form of swellable yarns with tensile strength. According to anotherembodiment of the cable the water-absorbent polymer can be employed as aswellable film. In another embodiment of the cable again, thewater-absorbent polymer can be employed as a moisture-absorbing core inthe centre of the cable. In the case of the cable, the substrate formsall the constituents of the cable which contain no water-absorbentpolymer. These include the conductors incorporated in the cable, such aselectrical conductors or light conductors, optical or electricalinsulating agents and constituents of the cable which ensure resistanceof the cable to mechanical stresses, such as braiding, woven fabric orknitted fabric of material of tensile strength, such as plastics andinsulations of rubber or other materials which prevent destruction ofthe outer skin of the cable.

If the composite is an absorbent core, the water-absorbent polymeraccording to the invention is incorporated into a substrate. Possiblesubstrates for the cores are chiefly preferably fibrous materialscomprising cellulose. In one embodiment of the core the water-absorbentpolymer is incorporated in an amount in the range from about 10 to about90, preferably from about 20 to about 80 and particularly preferablyfrom about 40 to about 70 wt. %, based on the core. In one embodiment ofthe core the water-absorbent polymer is incorporated into the core asparticles. In another embodiment of the core the water-absorbent polymeris incorporated into the core as fibres. The core can be produced on theone hand by a so-called airlaid process or by a so-called wetlaidprocess, a core produced by the airlaid process being preferred. In thewetlaid process the fibres or particles of water-absorbent polymer areprocessed to a nonwoven together with further substrate fibres and aliquid. In the airlaid process the fibres or particles ofwater-absorbent polymer and the substrate fibres are processed to anonwoven in the dry state. Further details are described in U.S. Pat.No. 5,916,670 and U.S. Pat. No. 5,866,242 for the airlaid process and inU.S. Pat. No. 5,300,192 for the wetlaid process.

In the wetlaid and airlaid process, in addition to the water-absorbentpolymer fibres or particles and the substrate fibres further suitableauxiliary substances known to the expert which contribute towardsconsolidation of the nonwoven obtained from this process can also beadded.

In the embodiment in which the composite is a diaper, the constituentsof the diaper which differ from the water-absorbent polymer according tothe invention represent the substrate of the composite. In a preferredembodiment the diaper comprises a core described above. In this case theconstituents of the diaper which differ from the core represent thesubstrate of the composite. In general a composite employed as a diapercomprises a water-impermeable under-layer, a water-permeable, preferablyhydrophobic upper layer, and a layer which comprises the water-absorbentpolymer and is arranged between the under-layer and the upper layer.This layer comprising the water-absorbent polymer is preferably a coredescribed above. The under-layer can contain all materials known to theexpert, polyethylene or polypropylene being preferred. The upper layercan likewise contain all suitable materials known to the expert,polyesters, polyolefins, viscose and the like being preferred, theseresulting in such a porous layer as to ensure an adequateliquid-permeability of the upper layer. The disclosure in U.S. Pat. No.5,061,295, U.S. Re. 26,151, U.S. Pat. No. 3,592,194, U.S. Pat. No.3,489,148 and U.S. Pat. No. 3,860,003 is referred to in this connection.

The invention furthermore relates to a process for the production of acomposite, wherein a water-absorbent polymer according to the inventionand a substrate and optionally a suitable auxiliary substance arebrought into contact with one another. They are preferably brought intocontact by the wetlaid and airlaid process, compacting, extrusion andmixing.

The invention also relates to a composite obtainable by the aboveprocess.

The invention furthermore relates to chemical products, preferablyfoams, shaped articles, fibres, foils, films, cable, sealing materials,liquid-absorbing hygiene articles, carriers for plant and fungusgrowth-regulating compositions, additives for building materials,packaging materials and soil additives, which comprise thewater-absorbent polymer according to the invention or the compositedescribed above.

The invention also relates to the use of the water-absorbent polymeraccording to the invention or of the composite described above inchemical products, preferably in foams, shaped articles, fibres, foils,films, cables, sealing materials, liquid-absorbing hygiene articles,carriers for plant and fungus growth-regulating compositions, additivesfor building materials, packaging materials, for controlled release ofactive compounds or in soil additives.

According to one embodiment according to the invention of the processaccording to the invention, the oxidized hydrocarbons according to theinvention, the polymers according to the invention and the usesaccording to the invention, it is preferable for the values of featuresaccording to the invention stated only with a lower limit to have anupper limit which has about 20 times, preferably about 10 times andparticularly preferably about 5 times the most preferred value of thelower limit.

The invention will now be explained in more detail with the aid of testmethods and non-limiting examples.

Test Methods

Gas Chromatography Analysis of Products in the Gas Phase

The gas chromatography analysis of products in the gas phase was carriedout with a Shimazu GC 14b gas chromatograph with a flame ionizationdetector and thermal conductivity detector. The gas phase to be analysedsubstantially comprised the gases propylene, O₂, N₂, CO₂, CO and thevolatile components of the liquid phase. Optimum separation of theindividual gaseous components was rendered possible by the followingcombination of apparatus parameters: Separating Porapak ® Q fromSUPELCO, Bellefonte, PA, columns USA (external diameter: ⅛ inch, lengthof the column for pre-separation: 0.4 m, length of the Porapak ® Qcolumn: 2.0 m, 80/100 mesh) Main column Carboxen 1000 from CS-CHROMATOGRAPHIE-SERVICE GmbH, Langerwehe (external diameter: ⅛ inch,length of the column: 5 m, 80/100 mesh) Carrier gas Helium Carrier gas 30 ml/min flow rate Volume of 100 μl the sample loop Temperature  8 minat 35° C., heated to 160° C. at 15° C./min, then programme kept at 160°C. for 4.7 min.Gas Chromatography Analysis of Products in the Liquid Phase

The analysis of the liquid phase was carried out with an HP 5890 seriesII gas chromatograph equipped with an FFAP capillary column from J&WSCIENTIFIC, Palo Alto, Calif., USA. Cyclohexanone was used as thestandard. The FFAP column had the following features: DB-FFAP, narrowbore, internal diameter 0.25 mm, length 30 m, film 0.25 μm.

Determination of the Propylene Conversion

At the end of the oxidation reaction the amount of unreacted propylenein the gas space (propylene(gas)) is determined by means of gaschromatography analysis. The propylene conversion [%] is defined asfollows:${{propylene}\quad{{conversion}\quad\lbrack\%\rbrack}} = {100 \times \left\{ \frac{\begin{matrix}{{{propylene}\quad{({in})\quad\lbrack{mmol}\rbrack}} -} \\{{propylene}\quad{({gas})\quad\lbrack{mmol}\rbrack}}\end{matrix}}{{propylene}\quad{({in})\quad\lbrack{mol}\rbrack}} \right\}}$

In this equation, propylene(in) is the molar amount of propyleneemployed at the start.

Determination of the Selectivity of the Oxidation Reaction

At the end of the oxidation reaction the amount of the individualoxidation products in the gas space or in the liquid phase is determinedby means of gas chromatography analysis. The amount of propylene reactedresults from the propylene conversion defined above. The selectivity [%]is defined as follows:$\text{selectivity~~[\%]} = {100 \times \left\{ \frac{\text{amount~~of~~component~~in~~question~~[mmol]}}{\text{amount~~of~~propylene~~(reacted)~~[mmol]}} \right\}}$Determination of the SCO Value

At the end of the oxidation reaction the amount of the individualoxidation products in the gas space or in the liquid phase is determinedby means of gas chromatography analysis. The SCO value of the palladiumcomplex in respect of the individual oxidation products is defined asfollows:${{SCO}\quad{{value}\quad\left\lbrack {g\text{/}g_{Pd}\text{/}h} \right\rbrack}} = {100 \times \left\{ \frac{\text{amount~~of~~component~~in~~question~~[g]}}{\text{amount~~of~~palladium~~[g]} \cdot \text{time~~[h]}} \right\}}$

EXAMPLES

To avoid the preparation of highly explosive mixtures in the autoclavefor safety reasons, the relative content of propylene and oxygen variesaccording to the choice of solvent employed. A high molar content ofpropylene compared with air is used if diglyme or a mixture of water anddiglyme is employed, since propylene is very readily soluble in diglyme.

In general, the autoclave is charged with an amount of propylene suchthat the pressure inside the autoclave is about 4.5 bar. Air is then fedin until a total pressure of about 18 bar is established inside theautoclave. The reaction is preferably carried out at a temperature ofabout 80° C. The results of experiments 1 to 8 and 9 to 12 are shown intables 1 and 2.

All the compounds employed in the following examples originate fromAcros, Belgium, unless stated otherwise.

Example 1

100 ml of a 1:1 mixture of water and diglyme is used as the liquidphase. 0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) and 0.053 g solid o-phenanthrolineare dissolved in the water/diglyme mixture and a pH of 9 is establishedwith 0.1 N aqueous NaOH solution. The solution obtained in this way isthen introduced into an autoclave of rustproof steel with a capacity of312 ml (stirred autoclave with a heatable jacket and a magnetic couplingfor the stirrer from Büchi Glas, Uster; 300 ml, max. 60 bar, max. 220°C.). The autoclave is closed and flushed a few times with helium (purity99.999%, Messer, Griesheim), with vigorous stirring (Eurostar digitalIKA stirrer, 1,000 rpm). 1.71 g (40.7 mmol) propylene and 3.46 g (119.8mmol) synthetic air (mixture of N₂ (purity 99.999%) and O₂ (purity99.999%) in a ratio of 79.5:20.5, Messer, Griesheim) are thenintroduced, a pressure of 17.8 bar being generated inside the autoclave(determined by an electronic pressure sensor from Wika und Setra,Klingenberg). The reactor is then heated up to a temperature of 80° C.(determined by a Haake® DC50/B3 thermostat with external temperaturecontrol by means of a Pt-100 thermocouple and a silicone oil bath).After 180 min the gas phase is let out and transferred into a 10 l gasbag (Linde, Wiesbaden) in order to stop the reaction, during which thetemperature in the reactor is kept at 80° C. The autoclave is flushed afew times with helium in order to collect the oxygen and unreactedpropylene dissolved in the liquid phase. The helium which has been usedfor the flushing is also transferred into the gas bag. The autoclave isthen allowed to cool to room temperature and the liquid phase isremoved. The autoclave is then washed out with water and this wash wateris combined with the aqueous phase. Both the aqueous phase diluted withthe wash water and the gas phase are then analysed by gaschromatography. The selectivity of the reaction is shown in table 1.

Example 2

The procedure of example 1 is repeated, 0.083 g Pd(O₂CCF₃)₂ (0.25 mmol)and 0.134 g solid bathophen-SO₃ (0.25 mmol) being employed as thecatalyst in this experiment. The pH is brought to 8.4 and the reactionis stopped after 120 minutes. The selectivity of the reaction is shownin table 1.

Example 3

The procedure of example 2 is repeated, exclusively water being used asthe liquid phase in this experiment. The pH is brought to 9 and thereaction is stopped after 180 minutes. The selectivity of the reactionis shown in table 1.

Example 4

The procedure of example 1 is repeated, 0.083 g Pd(O₂CCF₃)₂ (0.25 mmol)and 0.039 g solid 2,2′-dipyridyl (0.25 mmol) being employed as thecatalyst in this experiment. The pH is brought to 3.4 and the reactionis ended after 180 minutes. The selectivity of the reaction is shown intable 1. TABLE 1 Duration Propylene SCO value for the Selectivity of the[min]/T conversion acetone synthesis acetone synthesis Example [° C.][%] [g/g_(Pd)/h] [%] 1 180/80 59 4.21 64 2 120/80 70 17.5 83 3 180/80 3911.4 72 4 180/80 62 21.6 68

Example 5 (Comparison)

The procedure of example 1 is repeated, 100 ml water as the liquid phaseand 0.114 g Pd(O₂CCH₃)₂ (0.5 mmol) as the catalyst being employed inthis experiment. After flushing with nitrogen, 1.71 g (40.7 mmol)propylene and 3.46 g (119.8 mmol) air are added, a pressure of 17.8 barbeing obtained inside the autoclave. The pH was brought to 4. Thereaction was carried out at a temperature of 80° C. and was stoppedafter 181 minutes. The selectivity of the reaction is shown in table 2.

Example 6

The procedure of example 1 is repeated, 100 ml water as the liquid phaseand 0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst being employed inthis experiment. After flushing with nitrogen, 1.71 g (40.7 mmol)propylene and 3.46 g (119.8 mmol) air are added, a pressure of 17.8 barbeing obtained inside the autoclave. The pH was brought to 3.5. Thereaction was carried out at a temperature of 80° C. and was stoppedafter 192 minutes. The selectivity of the reaction is shown in table 2.

Example 7 (Comparison)

The procedure of example 1 is repeated, 100 ml diglyme as the liquidphase and 0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst being employedin this experiment. After flushing with nitrogen, 8.11 g (192.7 mmol)propylene and 3.01 g (104.4 mmol) air are added, a pressure of 18 barbeing obtained inside the autoclave. The autoclave was heated to atemperature of 80° C. After 83 minutes no reaction was to be observed.

Example 8

The procedure of example 1 is repeated, 100 ml of a 1:1 mixture (basedon the particular volume) of water and diglyme as the liquid phase and0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst being employed in thisexperiment. After flushing with nitrogen, 2.23 g (53.4 mmol) propyleneand 3.46 g (119.8 mmol) air are added, a pressure of 18 bar beingobtained inside the autoclave. The pH was brought to 3.5. The reactionwas carried out at a temperature of 80° C. and was stopped after 190minutes. The selectivity of the reaction is shown in table 2.

Example 9

The procedure of example 1 is repeated, 100 ml of a 3:1 mixture of waterand diglyme (based on the particular volume) as the liquid phase and0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst being employed in thisexperiment. After flushing with nitrogen, 2.09 g (49.7 mmol) propyleneand 3.42 g (118.6 mmol) air are added, a pressure of 18.2 bar beingobtained inside the autoclave. The pH was brought to 3.5. The reactionwas carried out at a temperature of 80° C. and was stopped after 172minutes. The selectivity of the reaction is shown in table 2.

Example 10

The procedure of example 1 is repeated, in this experiment 100 ml waterand 0.939 g (7 mmol) diglyme being employed as the liquid phase and0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst. After flushing withnitrogen, 1.93 g (45.9 mmol) propylene and 3.38 g (116.8 mmol) air areadded, a pressure of 18.1 bar being obtained inside the autoclave. ThepH was brought to 3.2. The reaction was carried out at a temperature of80° C. and was stopped after 173 minutes. The selectivity of thereaction is shown in table 2. It can be seen from the results of thisexperiment that even small amounts of diglyme in the liquid phase allowa selective oxidation of propylene to acrylic acid.

Example 11

The procedure of example 1 is repeated, 100 ml of a 1:1 mixture (basedon the particular volume) of water and diglyme as the liquid phase and0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst being employed in thisexperiment. After flushing with nitrogen, 2.10 g (49.4 mmol) propyleneand 3.43 g (119.0 mmol) air are added, a pressure of 17.7 bar beingobtained inside the autoclave. The pH was brought to 7.5. The reactionwas carried out at a temperature of 60° C. and was stopped after 170minutes. The selectivity of the reaction is shown in table 2.

Example 12

The procedure of example 1 is repeated, 100 ml of a 1:1 mixture (basedon the particular volume) of water and diglyme as the liquid phase and0.167 g Pd(O₂CCF₃)₂ (0.5 mmol) as the catalyst being employed in thisexperiment. 0.5 mmol sodium acetate was additionally added. Afterflushing with nitrogen, 2.26 g (53.7 mmol) propylene and 3.43 g (119.0mmol) air are added, a pressure of 18 bar being obtained inside theautoclave. The pH was brought to 3.6. The reaction was carried out at atemperature of 100° C. and was stopped after 150 minutes. Theselectivity of the reaction is shown in table 2. It can be seen from thecomparison of the results of experiments 8 and 12 that the addition ofsodium acetate increases the catalytic useful value of the palladiumcomplex containing ligands of the formula (I) and the selectivity of theoxidation of propylene to acrylic acid. TABLE 2 SCO value forSelectivity of the Duration Propylene the acrylic acid acrylic acid[min]/T conversion synthesis synthesis Example [° C.] [%] [g/g_(Pd)/h][%] 5 181/80 17.1 0.2 6.1 6 192/80 22.4 1.2 31.8 7  83/80 — — — 8 190/8024.2 2.9 53 9 172/80 26.2 2.9 48 10 173/80 25.9 1.6 29 11 170/60 21.61.6 30 12  150/100 28.3 3.2 40

1. A process for the oxidation of unsaturated hydrocarbons, wherein anunsaturated hydrocarbon, an oxygen-containing oxidizing agent, apalladium complex as the catalyst containing a ligand of the formula (I)

wherein R is a saturated, halogenated alkyl radical having from about 1to 20 carbon atoms, wherein the palladium complex contains, in additionto the ligand of the formula (I), an organic ligand (X∩Y) which containsat least two atoms X and Y of main group III, V or VI of the periodictable, wherein this ligand can be coordinated to palladium via at leastone of these two atoms X and Y and wherein at least one of these atomsis a constituent of a heterocyclic, aromatic ring system, and optionallyauxiliary substances are brought into contact with one another in aliquid phase based on (α1) from about 10 to about 100 wt. % of a proticpolar solvent and (α2) from 0 to about 90 wt. % of an aprotic polarsolvent, the sum of components (α1) and (α2) being about 100 wt. %, at atemperature in a range from about 30 to about 300° C. under a pressurein a range from about 1 to about 200 bar, such that a liquid phasecontaining oxygen-containing hydrocarbons is obtained.
 2. A process forthe oxidation of unsaturated hydrocarbons, wherein an unsaturatedhydrocarbon, an oxygen-containing oxidizing agent, a palladium complexas the catalyst containing a ligand of the formula (I)

wherein R is a saturated, halogenated alkyl radical having from about 1to about 20 carbon atoms, and optionally auxiliary substances arebrought into contact with one another in a liquid phase based on (α1)from about 40 to about 90 wt. % of a protic polar solvent and (α2) fromabout 10 to about 60 wt. % of an aprotic polar solvent selected from thegroup consisting of polyethylene glycol dialkyl ethers, polyethyleneglycol divinyl ethers and polyethylene glycol vinyl alkyl ethers, thesum of components (α1) and (α2) being about 100 wt. %, at a temperaturein a range from about 30 to about 300° C. under a pressure in a rangefrom about 1 to about 200 bar, such that a liquid phase containingoxygen-containing hydrocarbons is obtained.
 3. A process for theoxidation of unsaturated hydrocarbons, wherein an unsaturatedhydrocarbon, an oxygen-containing oxidizing agent, a palladium complexas the catalyst containing a ligand of the formula (I)

wherein R is a saturated, halogenated alkyl radical having from about 1to about 20 carbon atoms, and optionally auxiliary substances arebrought into contact with one another in a liquid phase based on (α1) aprotic polar solvent and (α2) an aprotic polar solvent, the weight ratioof the protic to the aprotic solvent being in a range from about100,000:1 to about 1:10, at a temperature in a range from about 30 toabout 300° C. under a pressure in a range from about 1 to about 200 bar,such that a liquid phase containing oxygen-containing hydrocarbons isobtained, the protic polar solvent not being water and the aprotic polarsolvent not being diglyme.
 4. A process for the oxidation of unsaturatedhydrocarbons, wherein an unsaturated hydrocarbon, an oxygen-containingoxidizing agent, a palladium complex as the catalyst containing a ligandof the formula (I)

wherein R is a saturated, halogenated alkyl radical having from about 1to about 20 carbon atoms, and optionally auxiliary substances arebrought into contact with one another in a liquid phase based on (α1)water and (α2) diglyme, the weight ratio of the water to the diglymebeing in a range from about 100,000:1 to about 1:10, at a temperature ina range from about 30 to about 300° C. under a pressure in a range fromabout 1 to about 200 bar, such that a liquid phase containingoxygen-containing hydrocarbons is obtained.
 5. The process according toclaim 1, wherein the radical R is a trifluoromethyl radical.
 6. Theprocess according to claim 1, wherein the oxygen-containing oxidizingagent is chosen from the group consisting of O₂, H₂O₂ and N₂O.
 7. Theprocess according to claim 1, wherein the liquid phase is a mixture ofwater and diglyme.
 8. The process according to claim 1, wherein theunsaturated hydrocarbon is propylene.
 9. The process according to claim1, wherein the palladium complex is first activated by reduction beforeit catalyses the oxidation of the unsaturated hydrocarbon.
 10. Theprocess according to claim 2, wherein the palladium complex contains, inaddition to the ligand of the formula (I), an organic ligand (X∩Y) whichcontains at least two atoms X and Y of main group III, V or VI of theperiodic table, wherein this ligand can be coordinated to palladium viaat least one of these two atoms X and Y and wherein at least one ofthese atoms is a constituent of a heterocyclic, aromatic ring system.11. The process according to claim 1, wherein the organic ligand (X∩Y)can be coordinated to palladium as a bidentate ligand via the two atomsX and Y.
 12. The process according to claim 1, wherein the organicligand (X∩Y) is selected from the group consisting ofp-bathophen-sulfonate and 2,2′-bipyridyl.
 13. The process according toclaim 1, wherein acetic acid or a salt of acetic acid is employed as theauxiliary substance.
 14. The process according to claim 13, wherein theacetic acid or a salt of acetic acid is employed as the auxiliarysubstance (δ1) to increase the catalytic useful value of the palladiumcomplex in the oxidation of unsaturated hydrocarbons, or (δ2) toincrease the selectivity of the oxidation of unsaturated hydrocarbons.15. A process for the preparation of water-soluble or water-absorbentpolymers, wherein, in a liquid phase obtained by a process for theoxidation of propylene, wherein propylene, an oxygen-containingoxidizing agent, a palladium complex as the catalyst containing a ligandof the formula (I)

wherein R is a saturated, halogenated alkyl radical having 1 to 20carbon atoms, and optionally auxiliaries are brought into contact withone another in a liquid phase based on (α1) from about 10 to about 100wt. % of a protic polar solvent and (α2) from 0 to about 90 wt. % of anaprotic polar solvent, the sum of components (α1) and (α2) being about100 wt. %, at a temperature in a range from about 30 to about 300° C.under a pressure in a range from about 1 to about 200 bar, the acrylicacid contained as the oxygen-containing hydrocarbon is polymerized andthe water-soluble or water-absorbent polymer obtained in this way isthen optionally dried and comminuted.